HELP! VR screen was stretched in Editor Runtime

After engine version upgrade to 4.25.3,I create a new VR project,play with VR, then screen was stretched like this: to fix this?Need help

I copied UE4Editor-Engine.dll from 4.25.1 To 4.25.3, replace the UE4Editor-Engine.dll, After then everything was back to normal.But I don’t know why…